Manufacture of hard covered books

ABSTRACT

A METHOD FOR BINDING HARD COVERED OR EDITION BOUND BOOKS WHEREIN THE HOT MELT ADHESIVE COMPOSITION WHICH IS UTILIZED COMPRISES A BLEND OF (A) A COPOLYMER OF ETHYLENE WITH EITHER VINYL ACETATE OR AN ALKYL ACRYLATE COMONOMER, (B) A TACKIFYING RESIN, (C) POLYETHYLENE, AND (D) A DILUENT. THE DESCRIBED COMPOSITIONS EXHIBIT A HIGH DEGREE OF PERMANENT SET WHICH IS PARTICULARLY USEFUL IN BINDING ROUNDED, HARD COVERED BOOKS.

United States Patent Ofiice 3,6l5,lil6

Patented Oct. 26, 1971 3,615,106 MANUFACTURE OF HARD COVERED BOOKSThomas P. Flanagan, Green Brook, and Paul P. Puletti, Glen Gardiner,N.J., assignors to National Starch and Chemical Corporation, New York,N.Y. No Drawing. Filed Apr. 4, 1969, Ser. No. 813,770 Int. Cl. (108i43/08 U.S. Cl. 281-21 Claims ABSTRACT OF THE DISCLOSURE A method forbinding hard covered or edition bound books wherein the hot meltadhesive composition which is utilized comprises a blend of (a) acopolymer of ethylene with either vinyl acetate or an alkyl acrylatecomonomer, (b) a tackifying resin. (c) polyethylene, and (d) a diluent.The described compositions exhibit a high degree of permanent set whichis particularly useful in binding rounded, hard covered books.

The manufacture of hard covered books involves unique features ofconstruction and operation which are not required in other methods ofbookbinding. Thus, in this operation, the pages are printed either inlong, continuous sheets or in individual sheets which are cut, foldedand properly arranged to form a series of stacks, referred to assignatures which are, in essence, a plurality of sheets. Thesesignatures are collected and then enclosed by means of end papers whichare typically adhered to the outer leaves of the first and lastsignatures. Thereafter, the signatures are transferred to sewingmachines where they are sewn individually and to one another. Adhesivesare then applied to the sewn edges of the signatures in a gluing offoperation which provides greater rigidity to the book body so as toenable it to withstand subsequent trimming and handling operations. Thebound signatures are then rounded, i.e. deformed such that a curvatureis impressed on the back edge of the book, backed and then lined-up in aprocedure which involves the application of hot glue to the roundedsurface and the attachment of a strip of fabric, usually crash, andbacking paper thereto. The books are then ready for the final casinginoperation wherein the hard cover is attached to the bound book.

Although the use of the hot metal adhesives has met with commercialsuccess in the binding of paper-backed books, i.e. soft covered books,wherein they have served to increase the rate of output, to eliminatethe stitching and stapling step, and to provide more permanent bindings,serious limitations have been encountered when attempts have been madeto use hot melts in the binding of hard covered books. These limitationshave been especially noted in the critical rounding step of the bindingoperation, i.e. the step wherein a curvature is impressed on the backedges of the book body and where the rear portions of the outermostsignatures are bent into a flange-like projection along each side of theback edge so that the cover boards may be closely fitted to theassembled body of leaves while permitting the hinge portions thereof tohave ample freedom of motion without exhibiting any tendency to becometorn or pulled out of place.

Currently available hot melt adhesives either: (1) provide adhesivefilms which are too rigid to be impressed into a rounded configurationor which split in the attempt, thereby losing their film continuity andenabling the pages to separate from the bound signatures; or, (2) theyprovide adhesive films which, although forming the desired roundedconfiguration, exhibit an excessive plastic flow. In the latterinstance, the excellent elastic memory exhibited by these films causesthem to abandon the required rounded configuration and to revert to theconfiguration which they assumed prior to the rounding operation.Therefore, since the critical rounded configuration is not provided ineither instance, it becomes obvious that the currently available hotmelt adhesives are not readily applicable for use in the binding ofrounded, hard covered books but, instead, must be limited for use in thepreparation of the undesirable square-backed, hard covered books.

It is the prime object of this invention to provide an adhesivecomposition which exhibits excellent adhesive strength and a high degreeof permanent set, thereby enabling it to be effectively utilized in thebinding of hard covered books. 4

It is still a further object that the adhesive be deposited by means ofapplicator equipment conventional in the bookbinding industry. Stillanother object is to provide an adhesive which may be handled in bulkform for use in the premelting equipment presently available in theindustry; or, which may be pelletized, diced, or granulated forconvenient premelting in an applicator of the extruder type; or, whichmay be utilized in rope or cord form for applicators designed to handleadhesives in the latter physical forms. Various other objects andadvantages of this invention will become apparent to the practitionerfrom the following detailed description thereof.

We have now discovered that by utilizing hot melt adhesive compositions,as hereinafter described, in the binding of hard covered books, it ispossible to overcome substantially all of the difficulties previouslyencountered in the binding of this type of book. Thus, the hot meltadhesives used in the process of this invention exhibit the rubberycharacteristics and adhesive strength which are essential to bind theindividual book pages. Furthermore, these hot melt adhesive productsdisplay good heat stability, rapid setting speed, and excellent adhesionto a variety of cellulosic and non-cellulosic materials such, forexample, as all types of paper stocks, waxed-glassine sheets, metallicfoils, polyester sheets, etc. Of particular importance, however, is thefact that these hot melts exhibit a high degree of permanent set. Thus,their adhesive films which serve to bind the books are capable of beingdeformed to correspond to the desired rounded configuration of the backof the book and, due to poor elastic memory, of permanently retainingthis rounded configuration. It is the combination of these essentialproperties in the hot melts of this invention that now permits themanufacture of quality, permanently bound, rounded, hard covered booksat high production speeds.

The hot melt adhesive compositions utilized in the process of thisinvention comprise a blend of: (a) from about 20 to 40%, by weight, of acopolymer of ethylene with one or more comonomers selected from thegroup consisting of vinyl acetate and the alkyl esters of acrylic acid,said copolymer representing the base polymer component of the hot meltsystem; (b) from about 15 to 45%, by weight, of at least one tackifyingresin which serves to extend the adhesive properties. of the hot meltsystem; (c) from about 5 to 15%, by weight, of polyethylene havingcertain specified characteristics which serves to lower the elasticmemory of the hot melt system; and, (d) from about 10 .to 40%, byweight, of a diluent which serves to reduce the melt viscosity orcohesive characteristics of the hot melt adhesive system withoutdecreasing its adhesive binding characteristics.

In more detail, the base polymer component of the adhesive systems is acopolymer of ethylene obtained by the polymerization of ethylene witheither vinyl acetate or one or more alkyl esters of acrylic acid whereinsaid alkyl group contains from 1 to about 4 carbon atoms. The ethylenecopolymers useful in the present hot melt adhesive compositions shouldcontain from about 70 to 85%, by weight, of ethylene.

The ethylene:vinyl acetate copolymers may be prepared by means ofprocedures well known to those skilled in the art, such, for example, asthe process described in U.S. Pat. 3,282,881. The ethylenezvinyl acetatecopolymers useful in the present adhesive compositions should have aninherent viscosity, as determined at 86 F. in a 0.25% solution of thecopolymer in toluene, of about 0.75 to 1.05 and a Melt Index, asdetermined by American Society for Testing Materials (ASTM) method D1238, within the range of from about 1.5 to 20.0.

The ethylenezalkyl acrylate copolymers are also prepared by means ofpolymerization procedures well known in the art. For example suchcopolymers can be prepared using 'free radical initiated polymerizationtechniques whereby a mixture of ethylene and an alkyl acrylate monomeris heated in the presence of a catalyst such as benzoyl peroxide, or anazo compound such as azobisisobutyronitrile, and the like. The proceduremay be carried out either batch-wise or continuously under pressuresranging from about 5,000 to about 50,000 pounds per square inch and attemperatures ranging from about 200 to about 580 F.

As noted hereinabove, suitable alkyl acrylate monomers which may becopolymerized with ethylene to form a copolymer component for use in thehot melt adhesives of the invention are those containing from 1 to about4 carbon atoms in their respective alkyl radicals. Examples of suchcomonomers are methyl acrylate, ethyl acrylate, propyl acrylate,isopropyl acrylate, butyl acrylate, and isobutyl acrylate. Theethylene:alkyl acrylate copolymers useful in these adhesive compositionsshould have an inherent viscosity, as determined at "86 F. in a 0.25%solution of the copolymer in toluene, of about 0.6 to 1.1 and a MeltIndex within the range of from about 1.0 to 20.0.

It is to be noted that, if desired, one or more ethylenicallyunsaturated carboxylic acids such, for example, as acrylic, methacrylic,fumaric, citraconic or itaconic acid, and the like, can be incorporatedinto the copolymers described above in a concentration such that theacid number of the resultant polymer is not greater than about 8. Theirpresence in such copolymers does not appreciably change the behavioralcharacteristics of the modified copolymers when utilized in the adhesiveblends of the subject process.

The tackifying resins which are present in the hot melt systems of thesubject process serve to extend the adhesive properties of thesedescribed hot melt systems. As contemplated in this invention, the termtackifying resin includes: 1) natural and modified rosins such, forexample, as gum rosin, wood rosin, tall-oil rosin, distilled rosin,hydrogenated rosin, dimerized rosin, and polymerized rosin; (2) glyceroland pentaerythritol esters of natural and modified rosins such, forexample, as the glycerol ester of pale wood rosin, the glycerol ester ofhydrogenated rosin, the glycerol ester of polymerized rosin, thepentaerythritol ester of hydrogenated rosin, and the phenolic-modifiedpentaerythritol ester of rosin; (3) polyterpene resins having asoftening point, as determined by ASTM method B 28-58 T, of from about176 to 302 F.; the latter polyterpene resins generally resulting fromthe polymerization of terpene hydrocarbons, such as the bicyclicmono-terpene known as pinene, in the presence of Friedel-Craftscatalysts at moderately low temperatures; (4) chlorinated biphenyl orterphenyl resins; (5) phenolic-modified terpene resins such, forexample, as the resin product resulting from the condensation in anacidic medium of a bicyclic terpene and phenol; and (6) aliphaticpetroleum hydrocarbon resins having a Ball and Ring softening point offrom about 176 to 257 R; an acid number of from about 0 to 2; asaponification value of less than about 1; and, an iodine value of fromabout 75-100. The latter class of tackifying resins are ordinarilyobtained during the polymerization of olefins and diolefins, and theymay comprise, for example, polymers based on the residual byproductmonomers produced during the manufacture of isoprene. Examples ofcommercially available resins of this type are Wing-Tack sold by theGoodyear Tire and Rubber Co. and the Sta-Tao and Betaprene H resins soldby Reichhold Chemicals, Inc.

The polyethylene component which functions as aforesaid to reduce theelastic memory of the adhesive composition must have a density rangingfrom about 0.91 to 0.96, as determined by ASTM method D 1505, and a MeltIndex ranging from about 1 to 200, as determined by ASTM method D 1238.It is to be noted that a high degree of permanent set is a particularlydesirable property of any hot melt composition which is to be used inthe binding of rounded, hard covered books and it is only by utilizingpolyethylene having these defined characteristics that we have been ableto provide hot melts displaying this useful property. Thus, the use ofpolyethylenes which do not fall within the above specified density andMelt Index ranges does not enhance the degree of permanent set of thehot melt compositions wherein they are present, and such formulationsare of little or no value in the preparation of rounded, hard coveredbooks. The so-called polyethylene greases which, as noted herein below,are useful as diluents in the present adhesive compositions wherein theyserve to reduce their viscosity, are to be particularly distinguishedfrom the polyethylene described hereinabove inasmuch as the presence ofthese polyethylene greases has no appreciable effect on the elasticmemory of the adhesives.

The distinction between polyethylene having this density from about 0.91to 0.96 and a Melt Index from about 1 to 200 and the polyethylenegreases are based upon their respective molecular weights. Thus, thepolyethylene resins useful in reducing the degree of elastic memory inthe adhesives of the invention should have a molecular weight of atleast about 10,000. On the other hand, the polyethylene greases havemolecular weights which are substantially below those of thepolyethylenes whose presence is required in our adhesive compositions.However, since it is extremely diflicult to determine the molecularweight of the higher molecular weight polyethylenes, various otherphysical constants are ordinarily used in describing these polymers. Forexample, the higher molecular weight polyethylenes required in ouradhesives are usually characterized in terms of their Melt Index whichcan be conveniently determined by means of ASTM method D 1238. However,the latter test procedure is inapplicable for use with the lowermolecular weight polyethylene greases since the greases are far toofluid to provide meaningful results with this test technique. For thisreason, these fluid low molecular wewight greases are usually describedin terms of their hardness values, softening points, molten viscosities,or actual molecular weights.

As previously stated, a diluent or mixture thereof is employed in ouradhesive systems in order to reduce the melt viscosity or cohesivecharacteristics of the hot melt adhesive compositions withoutappreciably decreasing its adhesive binding characteristics. Among theapplicable diluents are included: (1) low molecular weight, liquidpolybutylene in the range of from about 600 to 3000; (2) petroleum waxessuch as parafi in wax having a melting point of from about l30l65 F. andmicrocrystalline wax having a melting point of from about l40200 F.; thelatter melting points being determined by ASTM method D 127-60; (3)polyethylene greases or waxes having a softening point of from about176-230 F. and a hardness value, as determined by ASTM method D 1321, offrom about 2-100; (4) hydrogenated animal, fish and vegetable fats andoils such as hydrogenated tallow, lard, soya oil, cottonseed oil, castoroil, menhaden oil and cod liver oil, etc.; mineral oil; and, (6)synthetic waxes made by polymerizing carbon monoxide and hydrogen, suchas Fischer-Tropsch wax.

In addition to the above described components, the hot melt adhesivecompositions may contain various optional additives in order to modifycertain properties of the compositions for particular end-useapplications. Thus, optional additives which may be incorporated intothe hot melt compositions used in this invention include: antioxidantsor stabilizers, such as high molecular weight hindered phenolsincluding, for example, 1,3,5-trimethyl- 2,4,6-tris (3,5di-tert-butyl-4-hydroxybenzyl) benzene; 4,4'-thiobis (6tert-butyl-o-cresol); and, di-n-octadecyl3,S-di-tert-butyl-4-hydroxy-benzylphosphonate; pigments such as titaniumdioxide; and, fillers such as talc, clay, and the like.

The procedure for preparing these hot melt adhesive compositionsinvolves the melting of the tackifying resin and diluent in a steam oroil jacketed mixing kettle, preferably in a jacketed heavy duty mixer ofthe Baker Perkins or Day type, which is equipped with means formechanical agitation. The melting of the latter components is carriedout at temperatures of from about 250 to 350 F. The precise temperaturesused will depend, of course, on the melting points of the particulartackifying resin and diluent which are being employed. When the twocomponents are melted, the polyethylene and the ethylene copolymer areadded with sutficient agitation to avoid lumping. Stabilizers and otheroptional ingredients may also be added at this point. Mixing and heatingare continued until a smooth homogeneous mass is obtained whereupon theresulting hot melt adhesive is then withdrawn from the kettle in moltenform. The adhesive may be utilized immediately or, alternatively, it maybe extruded into rope form or converted into pellets, rods, slugs,cylinders, or billets, depending on the equipment which will besubsequently used to apply the adhesive during the binding operation; orit may be placed in cooling pans and held in bulk form for later use; orit may be granulated or diced.

The resulting hot melt adhesive compositions, as described hereinabove,are typically applied at temperatures of from about 300 to 400 F., and acorresponding melt viscosity of from about 5000 to 40,000 centipoises.Coatings having a wet film thickness of from about 5 to 30 mils areordinarily utilized in preparing the rounded, hard covered books bymeans of the process of this invention.

As previously noted, the basic technique for binding rounded, hardcovered books, as contemplated by the novel process of this invention,comprises the steps of: (1) printing, cutting, folding and enclosing thecollected signatures by means of end papers; (2) sewing the signaturesindividually and to one another; (3) applying the hot melt adhesivecomposition to the sewn edges of the signatures in a gluing offoperation; (4) allowing the adhesive to solidify at ambient temperaturesor by means of forced cooling; (5) rounding the bound signatures, i.e.mechanically deforming the backbone, and concurrently the front face, tothe shape commonly employed in the manufacture of hard covered books;(6) lining-up the bound sheets, i.e. applying crash or like fabric to afreshly applied hot melt adhesive coating which may or may not beidentical to the previously utilized hot melt composition; (7) enclosingthe bound sheets in endpapers or interlining, if such end-papers havenot previously been bound into the book body; and (8) casingin the boundbook within hard covers. As an alternative step, the crash or likematerial may be applied to the partially solidified hot melt coating ata point which is intermediate, timewise, between steps 3 and 4, ascontrasted with its more conventional application at step 6; the use ofthe latter sequence being dependent upon the particular bookbindingequipment that is being utilized. In either instance, this novelprocedure results in the preparation of rugged, durable, hard coveredbooks which are substantially free from such difliculties as loss oftheir rounded configuration and separation of their bound pages.

Although great emphasis has been placed, in this disclosure on the useof the described hot melt compositions in the binding of rounded, hardcovered books utilizing a gluing oif procedure, it should be noted thatthese adhesives may also be effectively utilized in the perfect binding,i.e. wherein sewing of the signatures is not required and the signaturefolds are cut so as to expose a fully squared backbone, of hard coveredbooks and soft covered books such as pocket books, magazines, catalogs,brochures, etc. Perfect bound, rounded, hard covered books can also bemanufactured.

The following examples will further illustrate the embodiment of thisinvention. In these examples all parts given are by Weight unlessotherwise noted.

EXAMPLE I This example illustrates the preparation of a hot meltadhesive composition typical of the products used in the process of thisinvention as well as the improved properties thereof which enable it tobe effectively utilized in the binding of hard covered books.

A heavy duty mixer which had been heated to 300 F. and which wasequipped with a stirring paddle was charged with 35 parts of apentaerythritol ester of rosin and 30 parts of microcrystalline waxhaving a melting point of 180 F. When the above components were melted,stirring was initiated and 7 parts of polyethylene having a density of0.95 and a Melt Index of 11 were added, followed by the addition of 28parts of an ethylenezvinyl acetate copolymer having a vinyl acetatecontent of 25%, by weight, and Melt Index of 2.0. Heating and stirringwere continued until a clear, homogeneous mass was obtained.

The resulting homogeneous hot melt composition had a melt viscosity of21,500 centipoises (cps) at 350 F., as determined by a Brookfieldviscoimeter using a #6 spindle at 20 rpm.

In order to demonstrate the applicability of the above prepared hot meltto book binding operations, it was subjected to the following testprocedures:

Low Temperature Flexibility The molten hot melt was cast, by means of aheated Bird applicator, onto a polytetrafiuoroethylene-coated steelplate yielding a film having a dry film thickness of 20 mils. Aftercooling, the film specimen was stripped from the plate and cut into /2 x2 inch test specimens. A representative specimen was then placed in atemperature controlled, carbon dioxide cabinet for a period of 10minutes whereupon it was immediately flexed at a 30 angle. Where thespecimen did not crack as a result of this procedure, a second identicalspecimen was placed in the cabinet at a lower temperature and theflexing procedure repeated. The temperature at which the specimeneventually cracked was thus viewed as its low temperature flexibilityvalue. Thus, as the latter value is decreased, there is a correspondingincrease in the flexibility and stability which can be expected uponexposing these films and the books bound therewith to low temperatureconditions.

Tensile Strength This property was determined on films cast from the hotmelts according to Test Method A of ASTM procedure D 882-56 T utilizingan lnstron Tensile Tester; the latter 7 films having been preparedaccording to the method set forth in the above described Low TemperatureFlexibility test.

The films derived from the hot melt adhesive composition of this exampleexhibited a Low Temperature Flexibility value of 10 to F. and a tensilestrength of 1,055 p.s.l.

Upon coating the above prepared molten hot melt composition onto thesewn edges of compressed signatures as part of a bookbinding process, anadhesive film was quickly formed, which upon setting or cooling,produced an excellent spine binding.

The above described properties of this hot melt composition thusindicate its usefulness in the binding of books.

EXAMPLE II In order to demonstrate the high degree of permanent setexhibited by the hot melt compositions described herein and, thereby,their applicability for use in bookbinding operations wherein roundingis a critical feature, each of the compositions, as describedhereinbelow, was subjected to a test procedure whereby it was cast, bymeans of a heated Bird applicator, onto a polytetrafiuoroethylenecoatedsteel plate yielding a film having a dry thickness of mils. Aftercooling, the film was stripped from the plate and cut into /2 by 2 inchtest specimens. Each specimen was then elongated to approximately 500%of its original length and, after the stress was relaxed, allowed toreach equilibrium for a period of 24 hours. The specimen was thenmeasured in order to determine the extent to which it had reverted toits original length.

The binding of rounded, hard covered books requires the use of hot meltadhesives exhibiting a low elastic memory and a low Percent Recoveryvalue, i.e. a value of about 25 to 55%, is preferred for such use. i

The procedure set forth in Example I, hereinabove, was utilized inpreparing each of the following hot melt compositions. The meltviscosity values at 350 F., as determined by a Brookfield viscosimeterusing a #6 spindle at 20 rpm, and the Low Temperature Flexibility andtensile strength, as determined by procedures described in Example I,hereinabove, are provided in order to characterize each of the thusprepared compositions with respect to their suitability for use asadhesives in a bookbinding process.

Composition A Parts Ethylenezethyl acrylate copolymer containing byweight, of ethyl acrylate and having a Melt Index of 2.5 PentaerythritolEster of Hydrogenated Wood Rosin (Ball and Ring S.P. 221 F.) 35Microcrystalline Wax, melting point 180 F. 30

Composition B Ethylene:ethyl acrylate copolymer containing 30%, byweight, of ethyl acrylate and having a Melt Index of 2.5 28Pentaerythritol ester of hydrogenated wood rosin (Ball and Ring S.P. 221F.) 35 Microcrystalline Wax, melting point 180 F 30 Polyethylene havinga density of 0.938 and a Melt Index of 8.0 7

Composition C Ethylenezvinyl acetate copolymer containing 18%, byweight, of ethyl acrylate and having a Melt Index of 2.5 28Pentaerythritol ester of hydrogenated wood rosin (Ball and Ring S.P. 221F.) 35 Microcrystalline wax, melting point 180 F. 30 Polyethylene havinga density of 0.938 and a Melt Index of 8.0 7

The following table summarizes the test results, including PercentRecovery values, obtained with films of the above described hot meltcompositions.

TABLE I Compositions A B C Melt Viscosity (cps) 350 F 11, 000 12,000 17,500 Low Temperature Flexibility, F 0 to 5 0 to 5 -5 to 0 TensileStrength (p.s.i.) 665 655 950 Percent Recovery, percent G1 55 30 EXAMPLEIII This example illustrates the preparation of a number of hot meltadhesive compositions useful in the process of this invention; thelatter compositions containing a variety of different components invarying proportions.

The procedure set forth in Example I, hereinabove, was utilized inpreparing each of the below described hot melt compositions. The meltviscosity values, Low Temperature Flexibility, tensile strength, andPercent Recovery values, determined as described hereinabove, areprovided in order to characterize each of the thus preparedcompositions.

Composition A Parts Ethylenezvinyl acetate copolymer containing 25%,

by weight, of vinyl acetate and having a Melt Index of 2.0 28Microcrystalline wax, melting point 180 F. 30 Alpha-pinene polymer (Balland Ring S.P. 239 F.) 35 Polyethylene having a density of 0.938 and 2.Melt Index of 8.0 7 1,3,5 trimethyl-2,4,6-tris(3,5-di-tert-butyl-4hydroxyi benzyl) benzene 0.1

This composition had the following properties:

Melt Viscosity-18,000 cps.

Low Temperature Flexibility-0 to 5 F. Tensile Strength935 p.s.i.

Percent Recovery25 Composition B The formulation of this composition wasthe same as that of Composition A, hereinabove, except that the polyterpene tackifying resin was replaced by an aliphatic petroleumhydrocarbon resin having a softening point of 212 F. This compositionhad the following properties:

Melt Viscosity-l0,875 cps.

Low Temperature Flexibility30 to 35 F. Tensile Strength-610 p.s.i.

Percent Recovery28%.

Composition C Parts Copolymer of Composition A 28 Microcrystalline wax,melting point 180 F. 5 Parafiin wax, melting point F 25 Pentaerythritolester of rosin 35 Polyethylene having a density of 0.95 and a Melt IndexThis composition had the' following properties:

Melt Viscosity17,250 cps. Low Temperature Flexibility-25 to 30 F.Tensile Strength-1,200 p.s.i. Percent Recovery-35%.

Composition D Parts Ethylene:vinyl acetate copolymer containing 25%, by

weight, of vinyl acetate and having a Melt Index of 6.0 28Microcrystalline wax, melting point 180 F 30 Aliphatic petroleumhydrocarbon resin having a softening point of 212 F 35 Polyethylenehaving a density of 0.92 and a Melt Index of 2.0 7

This composition had the following properties:

Melt Viscosity-16,000 cps. Low Temperature Flexibility25 to 30 F.Tensile Strength850 p.s.i. Percent Recovery33%.

Composition E Parts Copolymer of Composition A 30 Tackifying resin ofComposition D 35 Microcrystalline wax, melting point 180 F 30Polyethylene having a density of 0.938 and a Melt Index of 8.0

This composition had the following properties:

Melt Viscosityl2,750 cps.

Low Temperature Flexibility-25 to 30 F. Tensile Strength900 p.s.i.

Percent Recovery 28%.

Composition F The formulation of this composition was the same as thatof Composition A, hereinabove, except that the polyethylene used in thelatter example was replaced by a polyethylene having a density of 0.95and a Melt Index of 11.0. This composition had the following properties:

Melt Viscosity-24,700 cps.

Low Temperature Flexibility35 to 40 F. Tensile Strength870 p.s.i.

Percent Recovery25 Composition G The formulation of this composition wasthe same as that of Composition F, hereinabove, except that the ethylenecopolymer used in the latter formulation was replaced by anethylene-vinyl acetate copolymer containing 28%, by weight, of vinylacetate and having a Melt Index of 6.0. This composition had thefollowing properties:

Melt Viscosity-12,750 cps.

Low Temperature Flexibility-30 to 35 F. Tensile Strength690 p.s.i.

Percent Recovery-25 Upon coating each of the above described hot meltcompositions onto the sewn edges of compressed signatures, an adhesivefilm was quickly formed which, upon setting, produced an excellent spinebinding. The signatures were then deformed to produce a rounded back andthe above described hot melt compositions were again applied to the backprior to the application of crash. Excellent results were achieved inall cases.

EXAMPLE IV This example illustrates the critical change in theproperties displayed in a typical adhesive composition of this inventionwhen a polyethylene grease is substituted for the required polyethylenehaving a density of from 0.91 to 0.96 and a Melt Index of from 1 to 200.Formulations described in this example Were prepared by means of theprocedure set forth in Example I, hereinabove.

Composition A Parts Ethylenezvinyl acetate copolymer containing 28%, byweight, of vinyl acetate and having a Melt Index of 5.0 28Microcrystalline Wax, melting point 180 F. 30 Pentaerythritol ester ofrosin 35 Polyethylene having a density of 0.938 and a Melt Index of 8.010

Composition B This formulation was identical to Composition A,hereinabove except that the higher molecular weight polyethyleneutilized therein was replaced with a polyethylene grease having amolecular weight of only 2000 and a molten viscosity of 200 centipoisesat 140 C.

The resulting formulations displayed the following properties:

Composition Melt Viscosity (cps) 350 F 15,000 i, 250 Low TemperatureFlexibility, F 0 to 5 5 to 10 Tensile Strength (p.s.i.) 1,100 1,000Percent Recovery, percent 45 60 Thus, it is clearly evident that use ofa polyethylene grease as the polyethylene component of the adhesivecompositions of this invention results in the preparation of adhesiveswhich are characterized by an exceedingly low melt viscosity value andwhose Percent Recovery value, on the other hand, has been increased toan undesirably high level.

EXAMPLE V This example illustrates the preparation of two additionalvarieties of hot melt adhesive compositions suitable for use in theprocess of this invention. These compositions were prepared by theprocedure set forth in Example 'I, hereinabove.

Composition A Upon coating the above described hot melt compositionsonto the sewn edges of compressed signatures, adhesive films were formedwhich, upon setting, produced excellent spine bindings.

Summarizing, it is thus seen that this invention provides novel hot meltadhesives for an improved method for the binding of books. Variationsmay be made in proportions, procedures and materials without departingfrom the scope of this invention which is limited only by the followingclaims.

We claim:

1. A hot melt adhesive composition comprising a blend of: (1) from about20 to 40%, by weight, of a copolymer of ethylene with at least onecomonomer selected from the group consisting of vinyl acetate and thealkyl esters of acrylic acid, said copolymer containing from about 70 toby weight, of ethylene; (2) from about 1 1 15 to 45%, by weight, of atleast one tackifying resin selected from the group consisting of: (a)natural and modified rosins, (b) glycerol and pentaerythritol esters ofnatural and modified rosins, (c) polyterpene resins having an ASTMsoftening point of from about 176 to 302 F., (d) chlorinated biphenyl orterphenyl resins, (e) phenolicmodified terpene resins, and (f) aliphaticpetroleum hydrocarbon resins having a Ball and Ring softeningpoint offrom about 176 to 257 R, an acid number of from about to 2, asaponification value of less than about 1, and an iodine value of fromabout 75 to 100; (3) from about to by weight, of a polyethylene having adensity ranging from about 0.91 to 0.96 and a Melt Index ranging fromabout 1 to 200; and, (4) from about 10 to 40%, by weight, of a diluentselected from the group consisting of: (a) liquid polybutylene having amolecular weight in the range of from about 600 to 3000", (b) petroleumWaxes having a melting point of from about 130 to 200 F (c) polyethylenegreases and waxes having a softening point of from about 176 to 230 F.and an ASTM hardness value of, from about 2 to 100, (d) hydrogenatedanimal, fish and vegetable fats and oils, (e) mineral oil, and (f)Fischer-Tropsch Wax.

2. A hot melt adhesive composition comprising a blend of: (1) about 28parts, by weight, of an ethylenezvinyl acetate (72:28) copolymer; (2)about 35 parts, by weight, of a pentaerythritol ester of rosin; (3)about 10 parts, by Weight, of polyethylene having a density of 0.938 anda Melt Index of 8.0; and, (4) about 30 parts, by weight, ofmicrocrystalline Wax having a melting point of 180 F.

3. A hard covered book containing a plurality of sheets which are boundtoone another at the backbone of said book by means of the dried,consolidated residue of a hot melt adhesive composition comprising ablend of: (1) from about to 40%, by weight, of a copolymer of ethylenewith at least one comonomer selected from the group consisting of vinylacetate and the alkyl esters of acrylic acid, said copolymer containingfrom about 70 to 85%, by weight, of ethylene; (2) from about 15 to 45%,by weight, of at least one tackifying resin selected from the groupconsisting of: (a) natural and modified rosins, (b) glycerol andpentaerythritol esters of natural and modified rosins, (c) polyterpeneresins having an ASTM softening point of from about 176 to 302 F., (d)chlorinated biphenyl or terphenyl resins, (e) phenolic-modified terpeneresins, and (f) aliphatic petroleum hydrocarbon resins having a Ball andRing softening point of from about 176 to 257 R, an acid number offromabout 0 to 2, a-saponification value of less than about 1, and an iodinevalue of from about to '100; (3) from about 5 to 15 by Weight, of apolyethylene having a density ranging from about 0.91 to 0.96 and a Meltindex ranging from about 1 to 200; and, (4) from about 10 to 40%, byweight, of a diluent selected from the group consisting of: (a) liquidpoly-butylene having a molecular weight in the range of from about 600to 3000, (b) petroleum Waxes having a melting point of from about to 200F., (c) polyethylene greases and Waxes having a softening point of fromabout 176 to 230 F. and an ASTM hardness value of from about 2 to 100,(d) hydrogenated animal, fish and vegetable oils and fats and oils, (e)mineral oil, and (f) Fischer- Tropsch wax.

4. The hard covered book of claim 3, wherein said backbone of said bookhas a rounded configuration.

5. A hard covered book containing a plurality of sheets which are boundto one another at the backbone of said book by means of the dried,consolidated residue of a hot melt adhesive composition comprising ablend of: (1) about 28 parts, by Weight, of an ethylenezvinyl acetate(72:28) copolymer; (2) about 35 parts, by weight, of a pentaer ythritolester of rosin; (3) about 10 parts by Weight, of polyethylene having adensity of 0.938 and a Melt Index of 8.0; and, (4) about 30 parts byWeight, of microcrystalline wax having a melting point of 180 F.

References Cited UNITED STATES PATENTS 2,772,247 11/1956 Schroeder260897 X 3,084,128 4/ 1963 Stillwagon 2604 3,201,498 8/1965 Br'unson etal. 260897 3,223,436 12/1965 Becker 28121 3,282,881 11/1966 Flanagan26033.8 3,366,589 l/ 1968 Hammer et a1. 260897 X 3,448,178 6/1969'.Flanagan 260897 3,468,978 9/1969 Battersby 260897 3,485,783 12/1969 Kebe260897 X DONALD E. CZAJA, Primary Examiner D. J. BARRACK, AssistantExaminer US. Cl. X.R.

26023 AR, 23 H, 27 R, 27 EV, 28.5 AV, 28.5 A, 33.6 UA, 897 B

